Advanced FAT Repair - CGSecurity /**/ var skin = "monobook"; var stylepath = "/mw/skins"; var wgArticlePath = "/wiki/$1"; var wgScriptPath = "/mw"; var wgServer = "http://www.cgsecurity.org"; var wgCanonicalNamespace = ""; var wgNamespaceNumber = 0; var wgPageName = "Advanced_FAT_Repair"; var wgTitle = "Advanced FAT Repair"; var wgArticleId = 1389; var wgIsArticle = true; var wgUserName = null; var wgUserLanguage = "en"; var wgContentLanguage = "en"; /**/ Advanced FAT Repair From CGSecurity Jump to: navigation, search If the FAT boot sector is damaged, data can not be accessed. Windows will prompt The drive is not formatted, do you want to format it now? Linux mount will display wrong fs type, bad option, bad superblock TestDisk let you manipulate the boot sector of FAT partitions. In the Advanced menu, select the partition you want to modify and choose Boot. TestDisk 6.2-WIP, Data Recovery Utility, November 2005 Christophe GRENIER <[e-mail]> http://www.cgsecurity.org Disk /dev/sda - 120 GB / 111 GiB - CHS 14593 255 63 Partition Start End Size in sectors 1 * FAT32 0 1 1 1010 254 63 16241652 [NO NAME] 2 P Linux 1011 0 1 1023 254 63 208845 [/boot] 3 E extended LBA 1024 0 1 14592 254 63 217985985 5 L Linux RAID 1024 1 1 3573 254 63 40965687 [md0] X extended 3574 0 1 4210 254 63 10233405 6 L Linux RAID 3574 1 1 4210 254 63 10233342 [md1] X extended 4211 0 1 14592 254 63 166786830 7 L Linux 4211 1 1 14592 254 63 166786767 [ Type ] [ Boot ] [ Quit ] Boot sector recovery Contents 1 Repair FAT boot sector 1.1 Recover the FAT32 boot sector 1.2 Rebuild a valid FAT boot sector 1.3 Technical information about FAT boot sector rebuild 2 Repair FAT tables if (window.showTocToggle) { var tocShowText = "show"; var tocHideText = "hide"; showTocToggle(); } Repair FAT boot sector Recover the FAT32 boot sector TestDisk can use backup boot sector to fix corrupted FAT32 boot sector. The primary boot sector is sector zero of the filesystem, the backup FAT32 boot sector is located at sector 6. TestDisk checks the boot sector and the backup boot sector. If the boot sector and backup boot sector mismatches, you can overwrite the boot sector with the backup boot sector (Backup BS) or vice versa (Org. BS). Dump can used to display the sector content in both hexadecimal and ascii. Rebuild a valid FAT boot sector If there is no backup boot sector (FAT12, FAT16) or if the FAT32 boot sector is also corrupted, TestDisk can rebuild FAT boot sector, choose RebuildBS in the menu. TestDisk 6.2-WIP, Data Recovery Utility, November 2005 Christophe GRENIER <[e-mail]> http://www.cgsecurity.org Disk /dev/sda - 120 GB / 111 GiB - CHS 14593 255 63 Partition Start End Size in sectors 1 * FAT32 0 1 1 1010 254 63 16241652 [NO NAME] Boot sector OK Backup boot sector OK Sectors are identical. [ Quit ] [Rebuild BS][ Dump ] [Repair FAT] Return to Advanced menu Technical information about FAT boot sector rebuild To rebuild a FAT boot sector, TestDisk assumes that filesystem size is equal to partition size fragmentation is low The steps are select which FAT type are compatible with the filesystem size identify the sectors where begin the two FAT (number of reserved sector, fat length) and the FAT type (FAT12/16/32) If only one FAT is found: If FAT12 or FAT16 is found, assumes there is only one reserved sector. If it's the second FAT, deduce the the fat length. If beginning of FAT32 first fat is found at sector 32 or 33, deduce the number of reserved sectors. If two or more FAT sector beginning has been found: assumes the first two are the two copies of the FAT. Deduce the number of reserved sectors and fat length. If number of reserved sector or fat length hasn't been found, use inode of . directory entries to get the cluster size and deduce where the first cluster begin. From the number of cluster, deduce if it's a FAT12, FAT16 or FAT32. If FAT12 or FAT16, assume there is only one reserved sector. Try to find the number of directories entree (512 by default). Deduce the FAT length. If FAT12 or FAT16, find the root directory size Find the cluster size If FAT32, find the root cluster Create a boot sector with this information ask the user if he want to write this new boot sector or not, the user can also list the files of the FAT partition Repair FAT tables File Allocation Tables are maps of the data region, indicating which clusters are used by files and directories. To repair FAT, menu Repair FAT, TestDisk compares the two FAT copies. If FAT mismatches (sector by sector check) or contains errors, TestDisk uses the FAT copy with less errors and remove the obvious errors. This function must only be used on FAT filesystem with correct values in the boot sector. It has been used with success when scandisk, chkdsk or fsck.vfat refused to repair the filesystem or crashes. Back to Running the TestDisk Program Category: Data Recovery if (window.isMSIE55) fixalpha(); Data Recovery TestDisk PhotoRec download This page was last modified 21:03, 27 December 2006. Content is available under GNU Free Documentation License 1.2. if (window.runOnloadHook) runOnloadHook();